Electrochemical characterization of copper chemical mechanical planarization in KIO3 slurry

Abstract

Chemical mechanical polishing (CMP) of copper was performed using KIO3 as oxidizer and alumina particles as abrasives. For planarization of the surface morphology, the control of the surface passivation of Cu is critical during polishing. The copper removal rate decreased dramatically with increasing slurry pH without and with 0.1M KIO3. However, the removal rate is lower at pH 2 in slurry with 0.1M KIO3. The interaction between the Cu and the slurry was investigated by potentiodynamic and electrochemical impedance spectroscopy measurements under static condition. The electrochemical measurements revealed higher corrosion susceptibility at pH 2. XPS analysis indicates the severe precipitation of CuI on Cu at pH 2 in solution with 0.1M KIO3. The lower removal rate at pH 2 could be due to the reduced friction force of the pad with the precipitation of CuI on it. Atomic force microscopic (AFM) measurements were performed on both the etched surface and polished surface. It was shown that the surface roughness of the polished surfaces is better at pH 4 than that of pH 2.